Composition for providing an abrasion resistant coating on a substrate

ABSTRACT

Compositions having improved sability which, when applied to a variety of substrates and cured, form transparent coatings having superior abrasion resistant properties. The coating compositions are aqueous-organic solvent mixtures containing a mixture of hydrolysis products and partial condensates of an epoxy functional silane and a tetrafunctional silane and a multifunctional compound selected from the group consisting of multifunctional carboxylic acids, multifunctional anhydrides and combinations thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application U.S. Ser.No. 08/840,831, filed Apr. 17, 1997, entitled “COMPOSITION FOR PROVIDINGAN ABRASION RESISTANT COATING ON A SUBSTRATE”, now U.S. Pat. No.6,001,163.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to coating compositions, and moreparticularly but not by way of limitation, to coating compositionswhich, when cured, provide substantially transparent coatings havingenhanced abrasion resistance. In one aspect, the present inventionrelates to a coating composition having improved stability wherein thecoating compositions are derived from aqueous-organic solvent mixturescontaining effective amounts of epoxy functional silanes,tetrafunctional silanes and multifunctional compounds such asmultifunctional carboxylic acids, multifunctional anhydrides, andmixtures thereof.

2. Description of Prior Art

The prior art is replete with compositions which, when applied tosubstrates and cured, provide transparent, abrasion resistant coatingsfor the substrates. Such coatings are especially useful for polymericsubstrates where it is highly desirable to provide substrates withabrasion resistant surfaces, with the ultimate goal to provide abrasionresistant surfaces which are comparable to glass. While the compositionsof the prior art have provided transparent coating compositions havingimproved abrasion resistant properties, such prior art compositions aregenerally lacking when compared to glass. Thus, a need has long existedfor improved compositions having improved stability and which, whenapplied to a substrate, such as a polymeric substrate, and cured providetransparent, highly abrasion resistant coatings. It is to suchcompositions and processes by which such compositions are manufacturedand applied to substrates that the present invention is directed.

BRIEF SUMMARY OF THE INVENTION

The present invention provides compositions having improved stabilitywhich, when applied to a variety of substrates and cured, formtransparent coatings having superior abrasion resistant properties.Broadly, the coating compositions of the present invention comprise anaqueous-organic solvent mixture containing from about 10 to about 99.9weight percent, based on the total solids of the composition, of amixture of hydrolysis products and partial condensates of an epoxyfunctional silane and a tetrafunctional silane and from about 0.1 toabout 30 weight percent, based on the total solids of the composition,of a multifunctional compound selected from the group consisting ofmultifunctional carboxylic acids, multifunctional anhydrides andcombinations thereof. The epoxy functional silane and thetetrafunctional silane are present in the aqueous-organic solventmixture in a molar ratio of from about 0.1:1 to about 5:1. The coatingcompositions of the present invention may further include from about 0.1to about 50 weight percent of a mixture of hydrolysis products andpartial condensates of one or more silane additives, based on the totalsolids of the composition, and/or an amount of colloidal silica or ametal oxide or combinations thereof equivalent to from about 0.1 toabout 50 weight percent solids, based on the total solids of thecomposition.

It is an object of the present invention to provide coating compositionshaving improved stability which form transparent coatings upon curing.It is a further object of the present invention to provide stablecoating compositions which form transparent coatings upon curing havingimproved abrasion resistance.

Other objects, advantages and features of the present invention willbecome apparent upon reading the following detailed description inconjunction with the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to coating compositions having improvedstability which, when applied to a variety of substrates and cured, formsubstantially transparent abrasion resistant coatings having a Bayernumber of at least 5 when tested in accordance with the variation of theOscillating Sand Test (ASTM F735-81) hereinafter described.

For testing abrasion resistance of coated substrates, any of a number ofquantitative test methods may be employed, including the Taber Test(ASTM D-4060), the Tumble Test and the Oscillating Sand Test (ASTMF735-81). In addition, there are a number of qualitative test methodsthat may be used for measuring abrasion resistance, including the SteelWool Test and the Eraser Test. In the Steel Wool Tests and the EraserTest, sample coated substrates are scratched under reproducibleconditions (constant load, frequency, etc.). The scratched test samplesare then compared and rated against standard samples. Asemi-quantitative application of these test methods involves the use ofan instrument, such as a Spectrophotometer or a Colorimeter, formeasuring the scratches on the coated substrate as a haze gain.

The measured abrasion resistance of a cured coating on a substrate,whether measured by the Bayer Test, Taber Test, Steel Wool Test, EraserTest, Tumble Test, etc. is a function, in part, of the cure temperatureand cure time. In general, higher temperatures and longer cure timesresult in higher measured abrasion resistance. Normally, the curetemperature and cure time are selected for compatibility with thesubstrate; although, sometimes less than optimum cure temperatures andcure times are used due to process and/or equipment limitations. It willbe recognized by those skilled in the art that other variables, such ascoating thickness and the nature of the substrate, will also have aneffect on the measured abrasion resistance. In general, for each type ofsubstrate and for each coating composition there will be an optimumcoating thickness. The optimum cure temperature, cure time, coatingthickness, and the like, can be readily determined empirically by thoseskilled in the art.

Within the Ophthalmic Industry, the Oscillating Sand Test is presentlythe most widely used and accepted method for measuring abrasionresistance. Since the original ASTM application of the Oscillating SandTest was for testing flat polymeric sheets, the test method hasnecessarily been modified for use with ophthalmic lenses. There iscurrently no ASTM accepted standard (or other industry standard) forthis test as applied to ophthalmic lenses; therefore, there are a numberof basic variations of the Oscillating Sand Test in practice.

In one particular variation of the Oscillating Sand Test, a sand cradleis modified to accept coated sample lenses and uncoated referencelenses. Typically, poly(diethylene glycol-bis-allyl carbonate) lenses,hereinafter referred to as ADC lenses, are used as the reference lenses.The lenses are positioned in the cradle to allow a bed of abrasivematerial, either sand or a synthetically prepared metal oxide, to flowback and forth across the lenses, as the cradle oscillates back andforth at a fixed stroke, frequency and duration.

In the test method employed to determine the abrasion resistance of thecoating compositions of the present invention, a commercially availablesand sold by CGM, Inc., 1463 Ford Road, Bensalem, Pa., was used as theabrasive material. In this test, 877 grams of sifted sand (600 ml byvolume) was loaded into a 9 {fraction (5/16)}″×6 ¾″ cradle fitted withfour lenses. The sand was sifted through a #5 Mesh screen (A.S.T.M.E.-11specification) and collected on a #6 Mesh screen. Each set of fourlenses typically two ADC lenses and two coated lenses, was subjected toa 4 inch stroke (the direction of the stroke coinciding with the 9{fraction (5/16)}″ length of the cradle) at a frequency of 300 strokesper minute for a total of 3 minutes. The lens cradle was thenrepositioned by turning 180 degrees and then subjected to another 3minutes of testing. Repositioning of the cradle was used to reduce theimpact of any inconsistencies in the oscillating mechanism. The ADCreference lenses used were Silor 70 mm plano FSV lenses, purchasedthrough Essilor of America, Inc. of St. Petersburg, Fla.

The haze generated on the lenses was then measured on a Gardner XL-835Colorimeter. The haze gain for each lens was determined as thedifference between the initial haze on the lenses and the haze aftertesting. The ratio of the haze gain on the ADC reference lenses to thehaze gain on the coated sample lenses was then reported as the resultantabrasion resistance of the coating material. A ratio of greater than 1indicates a coating which provides greater abrasion resistance than theuncoated ADC reference lenses. This ratio is commonly referred to as theBayer ratio, number or value; the higher the Bayer number, the higherthe abrasion resistance of the coating. Coatings produced by curing thecoating compositions of the present invention, when tested using theOscillating Sand Test method as described above, coated on eitherpolycarbonate or on ADC lenses, have been shown to provide Bayer numberswhich exceed 5. For testing coated samples, samples coated on ADC lenseswere cured at a temperature of 120° C. for a period of 3 hours. Samplescoated on polycarbonate lenses were cured at a temperature of 129° C.for a period of 4 hours.

One who is skilled in the art will recognize that: (a) The descriptionsherein of coating systems which contain epoxy functional silanes,tetrafunctional silanes, silane additives which do not contain an epoxyfunctional group, and the multifunctional component refer to theincipient silanes and multifunctional components from which the coatingsystem is formed, (b) when the epoxy functional silanes, tetrafunctionalsilanes, and silane additives which do not contain an epoxy functionalgroup, are combined with the aqueous-solvent mixture, partial or fullyhydrolyzed species will result, (c) the resultant fully or partiallyhydrolyzed species will combine to form mixtures of multifunctionaloligomeric siloxane species, (d) these oligomers may or may not containboth pendant hydroxy and pendant alkoxy moieties and will be comprisedof a silicon-oxygen matrix which contains both silicon-oxygen siloxanelinkages and silicon-oxygen multifunctional component linkages, (e)these are dynamic oligomeric suspensions that undergo structural changeswhich are dependent upon a multitude of factors including; temperature,pH, water content, catalyst concentration, and the like.

The coating compositions of the present invention comprise anaqueous-organic solvent mixture containing from about 10 to about 99.9weight percent, based on the total solids of the composition, of amixture of hydrolysis products and partial condensates of an epoxyfunctional silane and a tetrafunctional silane and from about 0.1 toabout 30 weight percent, based on the total solids of the composition,of a multifunctional compound selected from the group consisting ofmultifunctional carboxylic acids, multifunctional anhydrides, andcombinations thereof. It will be recognized by those skilled in the artthat the amount of epoxy functional silane and the amount oftetrafunctional silane employed to provide the mixture of hydrolysisproducts and partial condensates of the epoxy functional silane and thetetrafunctional silane can vary widely and will generally be dependentupon the properties desired in the coating composition, the coatingformed by curing the coating composition, as well as the end use of thesubstrate to which the coating composition is applied. Generally,however, desirable results can be obtained where the epoxy functionalsilane and the tetrafunctional silane are present in the aqueous-solventmixture in a molar ratio of from about 0.1:1 to about 5:1. Moredesirably, the epoxy functional silane and the tetrafunctional silaneare present in the aqueous-solvent mixture in a molar ratio of fromabout 0.1:1 to about 3:1.

While the presence of water in the aqueous-organic solvent mixture isnecessary to form hydrolysis products of the silane components of themixture, the actual amount can vary widely. Essentially enough water isneeded to provide a substantially homogeneous coating mixture ofhydrolysis products and partial condensates of the epoxy functionalsilane and the tetrafunctional silane which, when applied and cured onan article, provides a substantially transparent coating with a Bayernumber of at least 5 when using the method hereinbefore described. Itwill be recognized by those skilled in the art that this amount of watercan be determined empirically.

The solvent constituent of the aqueous-organic solvent mixture of thecoating compositions of the present invention can be any solvent orcombination of solvents which is compatible with the epoxy functionalsilane, the tetrafunctional silane and the multifunctional component.For example, the solvent constituent of the aqueous-organic solventmixture may be an alcohol, an ether, a glycol or a glycol ether, aketone, an ester, a glycolether acetate and mixtures thereof. Suitablealcohols can be represented by the formula ROH where R is an alkyl groupcontaining from 1 to about 10 carbon atoms. Some examples of alcoholsuseful in the application of this invention are methanol, ethanol,propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiarybutanol, cyclohexanol, pentanol, octanol, decanol, and mixtures thereof.

Suitable glycols, ethers, glycol ethers can be represented by theformula R¹—(OR²)_(x)—OR¹ where x is 0, 1, 2, 3 or 4, R¹ is hydrogen oran alkyl group containing from 1 to about 10 carbon atoms and R² is analkylene group containing from 1 to about 10 carbon atoms andcombinations thereof.

Examples of glycols, ethers and glycol ethers having the above-definedformula and which may be used as the solvent constituent of theaqueous-organic solvent mixture of the coating compositions of thepresent invention are di-n-butylether, ethylene glycol dimethyl ether,propylene glycol dimethyl ether, propylene glycol methyl ether,dipropylene glycol methyl ether, tripropylene glycol methyl ether,dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether,ethylene glycol butyl ether, diethylene glycol butyl ether, ethyleneglycol dibutyl ether, ethylene glycol methyl ether, diethylene glycolethyl ether, diethylene glycol dimethyl ether, ethylene glycol ethylether, ethylene glycol diethyl ether, ethylene glycol, diethyleneglycol, triethylene glycol, propylene glycol, dipropylene glycol,tripropylene glycol, butylene glycol, dibutylene glycol, tributyleneglycol and mixtures thereof. In addition to the above, cyclic etherssuch as tetrahydrofuran and dioxane are suitable ethers for theaqueous-organic solvent mixture.

Examples of ketones suitable for the aqueous-organic solvent mixture areacetone, diacetone alcohol, methyl ethyl ketone, cyclohexanone, methylisobutyl ketone and mixtures thereof.

Examples of esters suitable for the aqueous-organic solvent mixture areethyl acetate, n-propyl acetate, n-butyl acetate and combinationsthereof.

Examples of glycolether acetates suitable for the aqueous-organicsolvent mixture are propylene glycol methyl ether acetate, dipropyleneglycol methyl ether acetate, ethyl 3-ethoxypropionate, ethylene glycolethyl ether acetate and combinations thereof.

The epoxy functional silane useful in the formulation of the coatingcompositions of the present invention can be any epoxy functional silanewhich is compatible with the tetrafunctional silane and themultifunctional component of the coating composition and which providesa coating composition which, upon curing, produces a substantiallytransparent, abrasion resistant coating having a Bayer number of atleast about 5 when employing the test method hereinbefore described.Generally, such epoxy functional silanes are represented by the formulaR³ _(x)Si(OR⁴)_(4−x) where x is an integer of 1, 2 or 3, R³ is H, analkyl group, a functionalized alkyl group, an alkylene group, an arylgroup, an alkyl ether, and combinations thereof containing from 1 toabout 10 carbon atoms and having at least 1 epoxy functional group, andR⁴ is H, an alkyl group containing from 1 to about 5 carbon atoms, anacetyl group, a —Si(OR⁵)_(3−y)R⁶ _(y) group where y is an integer of 0,1, 2, or 3, and combinations thereof where R⁵ is H, an alkyl groupcontaining from 1 to about 5 carbon atoms, an acetyl group, or another—Si(OR⁵)_(3−y)R⁶ _(y) group and combinations thereof, and R⁶ is H, analkyl group, a functionalized alkyl group, an alkylene group, an arylgroup, an alkyl ether, and combinations thereof containing from 1 toabout 10 carbon atoms which may also contain an epoxy functional group.

Examples of such epoxy functional silanes areglycidoxymethyltrimethoxysilane, 3-glycidoxypropyltrihydroxysilane,3-glycidoxypropyldimethylhydroxysilane,3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,3-glycidoxypropyldimethoxymethylsilane,3-glycidoxypropyldimethylmethoxysilane,3-glycidoxypropyltributoxysilane,1,3-bis(glycidoxypropyl)tetramethyldisiloxane,1,3-bis(glycidoxypropyl)tetramethoxydisiloxane,1,3-bis(glycidoxypropyl)-1,3-dimethyl-1,3-dimethoxydisiloxane,2,3-epoxypropyltrimethoxysilane, 3,4-epoxybutyltrimethoxysilane,6,7-epoxyheptyltrimethoxysilane, 9,10-epoxydecyltrimethoxysilane,1,3-bis(2,3-epoxypropyl)tetramethoxydisiloxane,1,3-bis(6,7-epoxyheptyl)tetramethoxydisiloxane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and the like.

The tetrafunctional silanes useful in the formulation of the coatingcompositions of the present invention are represented by the formulaSi(OR⁷)₄ where R⁷ is H, an alkyl group containing from 1 to about 5carbon atoms and ethers thereof, an (OR⁷) carboxylate a —Si(OR⁸)₃ groupwhere R⁸ is a H, an alkyl group containing from 1 to about 5 carbonatoms and ethers thereof, an (OR³carboxylate or another —Si(OR⁸)₃ groupand combinations thereof. Examples of tetrafunctional silanesrepresented by the formula Si(OR⁷)₄ are tetramethyl orthosilicate,tetraethyl orthosilicate, tetrapropyl orthosilicate, tetraisopropylorthosilicate, tetrabutyl orthosilicate, tetraisobutyl orthosilicate,tetrakis(methoxyethoxy)silane, tetrakis(methoxypropoxy)silane,tetrakis(ethoxyethoxy)silane, tetrakis(methoxyethoxyethoxy)silane,trimethoxyethoxysilane, dimethoxydiethoxysilane, triethoxymethoxysilane,poly(dimethoxysiloxane), poly(diethoxysiloxane),poly(dimethoxydiethoxysiloxane), tetrakis(trimethoxysiloxy)silane,tetrakis(triethoxysiloxy)silane, and the like. In addition to the R⁷ andR⁸ substituants described above for the tetrafunctional silane, R⁷ andR⁸ taken with oxygen (OR⁷) and (OR⁸) can be carboxylate groups. Examplesof tetrafunctional silanes with carboxylate functionalities are silicontetracetate, silicon tetrapropionate and silicon tetrabutyrate.

The multifunctional compounds which can be employed in the formulationof the coating compositions of the present invention can be anymultifunctional carboxylic acid, multifunctional anhydride andcombinations thereof which is compatible with the epoxy functionalsilane and the tetrafunctional silans of the coating compositions andwhich is capable of interacting with the hydrolysis products and partialcondensates of the epoxy functional silane and the tetrafunctionalsilane to provide a coating composition which, upon curing, produces asubstantially transparent, abrasion resistant coating having a Bayernumber of at least 5 when employing the test method hereinbeforedescribed.

Examples of multifunctional carboxylic acids which can be employed asthe multifunctional compound in the compositions of the presentinvention include malic acid, aconitic acid (cis,trans), itaconic acid,succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid,suberic acid, azelaic acid, sebacic acid, cyclohexyl succinic acid,1,3,5 benzene tricarboxylic acid, 1,2,4,5 benzene tetracarboxylic acid,1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,1-cyclohexanediacetic acid, 1,3-cyclohexanediacetic acid,1,3,5-cyclohexanetricarboxylic acid and unsaturated dibasic acids suchas fumaric acid and maleic acid and combinations thereof.

Examples of multifunctional anhydrides which can be employed as themultifunctional compound in the coating compositions of the presentinvention include the cyclic anhydrides of the above mentioned dibasicacids such as succinic anhydride, itaconic anhydride, glutaricanhydride, trimellitic anhydride, pyromellitic anhydride, phthalicanhydride and maleic anhydride and combinations thereof.

The nature of the interaction between the epoxy functional silane, thetetrafunctional silane and the multifunctional compound, and the effectthat such interaction has on the abrasion resistance of the curedcoating is not fully understood. It is believed, however, that themultifunctional compound acts as more than just a hydrolysis catalystfor the silanes. In this regard, it can be proposed that themultifunctional compound has specific activity towards the epoxyfunctionality on the silane. The reaction of the epoxy groups withcarboxylic acids is well known and can occur under either acidic orbasic conditions. The carboxylate groups on the multifunctional compoundwill also most likely have some activity towards the silicon atoms inthe matrix; and such interaction may be through normal exchangereactions with residual alkoxide and hydroxide groups or, alternatively,through some hypervalent state on the silicon atoms. The actualinteraction involving the multifunctional compound may, in fact, be acombination of all of the above possibilities, the result of which wouldbe a highly crosslinked matrix. Thus, the matrix is enhanced throughextended linkages involving the multifunctional compound.

As examples of the significance of these possible interactions, coatingsprepared with non-multifunctional compounds, for example acetic acid,fail to show the same high degree of stability and abrasion resistanceas obtained through the use of the multifunctional compounds. In thiscase, a non-multifunctional acid would have the same utility in thecoating composition as a hydrolysis catalyst for the silanes, but couldnot provide the extended linkages presumed to be possible with themultifunctional compounds.

The coating compositions of the present invention are also very stablewith respect to aging, both in terms of performance and solutionstability. The aging of the coating compositions is characterized by agradual increase in viscosity which eventually renders the coatingcompositions unusable due to processing constraints. Aging studies haveshown that the coating compositions of the present invention, whenstored at temperatures of 5° C. or lower, have usable shelf lives of 3-4months. During this period, the abrasion resistance of the curedcoatings does not significantly decrease with time. Further, suchstudies have shown that stability of the coating compositions isdependent on the relative concentrations of the epoxy functional silane,the tetrafunctional silane and the multifunctional compound. In general,higher concentrations of the epoxy functional silane and themultifunctional compound contribute to increased stability of thecoating mixture. Thus, in addition to providing enhanced abrasionresistance to the cured coatings, the multifunctional compoundcontributes to the overall stability of the coating compositions.

While the coating compositions produced by the unique combination of anepoxy functional silane, a tetrafunctional silane and a multifunctionalcompound provide the primary basis for the high abrasion resistance ofcoatings prepared by curing such coating compositions, the coatingcompositions may additionally include other materials to: (a) enhancethe stability of the coating compositions; (b) increase the abrasionresistance of cured coatings produced by the coating compositions; (c)enhance processing of the coating compositions; and (d) provide otherdesirable properties of the cured coating produced from the coatingcompositions.

The coating compositions of the present invention may further includefrom about 0.1 to about 50 weight percent, based on the weight of totalsolids of the coating compositions, of a mixture of hydrolysis productsand partial condensates of one or more silane additives (i.e,trifunctional silanes, difunctional silanes, monofunctional silanes, andmixtures thereof. The silane additives which can be incorporated intothe coating compositions of the present invention have the formula R⁹_(x)Si(OR¹⁰)_(4−x) where x is a number of 1, 2 or 3; R⁹ is H, or analkyl group containing from 1 to about 10 carbon atoms, a functionalizedalkyl group, an alkylene group, an aryl group an alky ether group andcombinations thereof; R¹⁰ is H, an alkyl group containing from 1 toabout 10 carbon atoms, an acetyl group; and combinations thereof.Examples of silane additives represented by the above-defined formulaare methyltrimethoxysilane, ethyltrimethoxysilane,propyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane,hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane,cyclohexyltrimethoxysilane, cyclohexylmethyltrimethoxysilane,3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane,allyltrimethoxysilane, dimethyldimethoxysilane,2-(3-cyclohexenyl)ethyltrimethoxysilane, 3-cyanopropyltrimethoxysilane,3-chloropropyltrimethoxysilane, 2-chloroethyltrimethoxysilane,phenethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane,3-aminopropyltrimethoxysilane, phenyltrimethoxysilane,3-isocyanopropyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,4-(2-aminoethylaminomethyl)phenethyltrimethoxysilane,chloromethyltriethoxysilane, 2-chloroethyltriethoxysilane,3-chloropropyltriethoxysilane, phenyltriethoxysilane,ethyltriethoxysilane, propyltriethoxysilane, butyltriethoxysilane,isobutyltriethoxysilane, hexyltriethoxysilane, octyltriethoxysilane,decyltriethoxysilane, cyclohexyltriethoxysilane,cyclohexylmethyltriethoxysilane, 3-methacryloxypropyltriethoxysilane,vinyltriethoxysilane, allyltriethoxysilane,[2-(3-cyclohexenyl)ethyltriethoxysilane, 3-cyanopropyltriethoxysilane,3-methacrylamidopropyltriethoxysilane, 3-methoxypropyltrimethoxysilane,3-ethoxypropyltrimethoxysilane, 3-propoxypropyltrimethoxysilane,3-methoxyethyltrimethoxysilane, 3-ethoxyethyltrimethoxysilane,3-propoxyethyltrimethoxysilane,2-[methoxy(polyethyleneoxy)propyl]heptamethyltrisiloxane,[methoxy(polyethyleneoxy)propyl]trimethoxysilane,[methoxy(polyethyleneoxy)ethyl]trimethoxysilane,[methoxy(polyethyleneoxy)propyl]-triethoxysilane,[methoxy(polyethyleneoxy)ethyl]triethoxysilane.

The selection of the silane additive, as well as the amount of suchsilane additive incorporated into the coating compositions will dependupon the particular properties to be enhanced or imparted to either thecoating composition or the cured coating composition. For example, whenthe difunctional silane dimethyldimethoxysilane is utilized as thesilane additive and incorporated into the coating composition in anamount of about 10% or less, based on the total solids of thecomposition, the viscosity increase is greatly reduced during aging ofthe coating composition, without greatly affecting the resultantabrasion resistance of the cured coating.

In certain applications, it is useful to add colloidal silica to thecoating composition. Colloidal silica is commercially available under anumber of different tradename designations, including Nalcoag® (NalcoChemical Co., Naperville, Ill.); Nyacol® (Nyacol Products, Inc.,Ashland, Md.); Snowtex® (Nissan Chemical Industries, LTD., Tokyo,Japan); Ludox® (DuPont Company, Wilmington, Del.); and Highlink OG®(Hoechst Celanese, Charlotte, N.C.). The colloidal silica is an aqueousor organic solvent dispersion of particulate silica and the variousproducts differ principally by particle size, silica concentration, pH,presence of stabilizing ions, solvent makeup, and the like. It isunderstood by those skilled in the art that substantially differentproduct properties can be obtained through the selection of differentcolloidal silicas.

Colloidal silica, when added to a coating composition, is considered areactive material. The surface of the silica is covered with siliconbound hydroxyls, some of which are deprotonated, which can interact withmaterials in the coating composition. The extent of these interactionsis dictated by a variety of factors, including solvent system, pH,concentration, and ionic strength. The manufacturing process furtheraffects these interactions. It is thus recognized by those skilled inthe art, that colloidal silica can be added into a coating formulationin different ways with different results.

In the coating compositions of the present invention, colloidal silicacan be added into the coating compositions in a variety of differentways. In some instances, it is desirable to add the colloidal silica inthe last step of the reaction sequence. In other instances, colloidalsilica is added in the first step of the reaction sequence. In yet otherinstances, colloidal silica can be added in an intermediate step in thesequence.

It has been observed that the addition of colloidal silica to thecoating compositions of the present invention can further enhance theabrasion resistance of the cured coating compositions and can furthercontribute to the overall stability of the coating compositions. Themost significant results have been achieved with the use of aqueousbasic colloidal silica, that is, aqueous mixtures of colloidal silicahaving a pH greater than 7. In such cases, the high pH is accompanied bya higher concentration of a stabilizing counterion, such as the sodiumcation. Cured coatings formulated from the coating compositions of thepresent invention which contain basic colloidal silicas have shownabrasion resistance comparable to those of a catalyzed coatingcomposition of the present invention (that is, a composition ofhydrolysis products and partial condensates of an epoxy functionalsilane, a tetrafunctional silane, a multi-functional compound and acatalyst such as sodium hydroxide), but the coating compositionscontaining colloidal silica have enhanced stability with respect to thecatalyzed compositions which do not contain colloidal silica.

In the same manner, it is also possible to add other metal oxides intothe coating compositions of the present invention. Such additions may bemade instead of, or in addition to, any colloidal silica additions.Metal oxides may be added to the inventive coatings to provide orenhance specific properties of the cured coating, such as abrasionresistance, refractive index, anti-static, anti-reflectance,weatherability, etc. It will be recognized by those skilled in the artthat similar types of considerations that apply to the colloidal silicaadditions will also apply more generally to the metal oxide additions.

Examples of metal oxides which may be used in the coating compositionsof the present invention include silica, zirconia, titania, ceria, tinoxide and mixtures thereof.

The amount of colloidal silica incorporated into the coatingcompositions of the present invention can vary widely and will generallydepend on the desired properties of the cured coating produced from thecoating compositions, as well as the desired stability of the coatingcompositions. Similarly, the amount of metal oxides incorporated intothe coating compositions of the present invention can vary widely andwill generally depend on the desired properties of the cured coatingproduced from the coating compositions, as well as the desired stabilityof the coating compositions.

When colloidal silica and/or metal oxides are added, it is desirable toadd from about 0.1 to about 50 weight percent of solids of the colloidalsilica and/or metal oxides, based on the total solids of thecomposition, to the coating compositions of the present invention. Thecolloidal silica and/or metal oxides will generally have a particle sizein the range of 2 to 150 millimicrons in diameter, and more desirably, aparticle size in the range of from about 2 to 50 millimicrons.

Although a catalyst is not an essential ingredient of the presentinvention, the addition of a catalyst can affect abrasion resistance andother properties of the coating including stability, tinting capacity,porosity, cosmetics, caustic resistance, water resistance and the like.The amount of catalyst used can vary widely, but when present willgenerally be in an amount sufficient to provide from about 0.1 to about10 weight percent, based on the total solids of the composition.

Examples of catalysts which can be incorporated into the coatingcompositions of the present invention are (i) metal acetylacetonates,(ii) diamides, (iii) imidazoles, (iv) amines and ammonium salts, (v)organic sulfonic acids and their amine salts, (vi) alkali metal salts ofcarboxylic acids, (vii) alkali metal hydroxides and (viii) fluoridesalts. Thus, examples of such catalysts include for group (i) suchcompounds as aluminum, zinc, iron and cobalt acetylacetonates; group(ii) dicyandiamide; for group (iii) such compounds as 2-methylimidazole,2-ethyl-4-methylimidazole and 1-cyanoethyl-2-propylimidazole; for group(iv), such compounds as benzyldimethylamine, and 1,2-diaminocyclohexane;for group (v), such compounds as trifluoromethanesulfonic acid; forgroup (vi), such compounds as sodium acetate, for group (vii), suchcompounds as sodium hydroxide, and potassium hydroxide; and for group(viii), tetra n-butyl ammonium fluoride, and the like.

An effective amount of a leveling or flow control agent can beincorporated into the composition to more evenly spread or level thecomposition on the surface of the substrate and to provide substantiallyuniform contact with the substrate. The amount of the leveling or flowcontrol agent can vary widely, but generally is an amount sufficient toprovide the coating composition with from about 10 to about 5,000 ppm ofthe leveling or flow control agent. Any conventional, commerciallyavailable leveling or flow control agent which is compatible with thecoating composition and the substrate and which is capable of levelingthe coating composition on a substrate and which enhances wettingbetween the coating composition and the substrate can be employed. Theuse of leveling and flow control agents is well known in the art and hasbeen described in the “Handbook of Coating Additives” (ed. Leonard J.Calbo, pub. Marcel Dekker), pg 119-145.

Examples of such leveling or flow control agents which can beincorporated into the coating compositions of the present inventioninclude organic polyethers such as TRITON X-100, X-405, N-57 from Rohmand Haas, silicones such as Paint Additive 3, Paint Additive 29, PaintAdditive 57 from Dow Corning, SILWET L-77, and SILWET L-7600 from OSiSpecialties, and fluorosurfactants such as FLUORAD FC-171, FLUORADFC-430 and FLUORAD FC-431 from 3M Corporation.

In addition, other additives can be added to the coating compositions ofthe present invention in order to enhance the usefulness of the coatingcompositions or the coatings produced by curing the coatingcompositions. For example, ultraviolet absorbers, antioxidants, and thelike can be incorporated into the coating compositions of the presentinvention, if desired.

The coating compositions of the present invention can be prepared by avariety of processes to provide stable coating compositions which, uponcuring, produce substantially transparent coatings having enhancedabrasion resistance. For example, the epoxy functional silane, thetetrafunctional silane and the multifunctional compound can be added tothe aqueous-organic solvent solution and stirred for a period of timeeffective to produce a coating composition having improved stability.When cured, such coating compositions have Bayer numbers ranging fromabout 6 to about 8 when employing the test method hereinbeforedescribed. However, by incorporating a catalyst into the aqueous-organicsolvent mixtures containing the epoxy functional silane, thetetrafunctional silane and the multifunctional compound, the Bayernumbers of the cured coatings produced from such coating compositionsare increased so as to range from about 8 to about 15 when employing thetest method hereinbefore described.

When an aqueous hydrolyzate of the epoxy functional silane is mixed witha solution of the multifunctional compound and combined with thetetrafunctional silane a coating composition is formed which when curedhas a Bayer value of about 7 when employing the test method hereinbefore described.

When a tetrafunctional silane hydrolyzate is formed in the presence ofthe multifunctional compound or other acid and the aqueous-organicmixture, and the epoxy functional component is added to this mixture, acoating composition is obtained which when cured provides a Bayer valueof about 7 when employing the test method herein before described.

When a mixture of the tetrafunctional silane and the multifunctionalcompound is hydrolyzed and treated with an effective amount of sodiumhydroxide and then admixed with an aqueous hydrolyzate of the epoxyfunctional silane, the resulting cured coating composition has a Bayervalue of about 14 when employing the test method herein beforedescribed.

From the above, it becomes clear to those skilled in the art thatvarious methods can be employed for producing the coating compositionsof the present invention, and that such compositions, when cured,provide coatings having improved abrasion resistance. Further, thecoating compositions have a desired stability which enhances theirusefulness. However, by altering the method of preparing suchcompositions, product properties, such as stability and abrasionresistance, i.e., Bayer number, can be affected.

The compositions of the invention can be applied to solid substrates byconventional methods, such as flow coating, spray coating, curtaincoating, dip coating, spin coating, roll coating, etc. to form acontinuous surface film. Any substrate compatible with the compositionscan be coated with the compositions, such as plastic materials, wood,paper, metal, printed surfaces, leather, glass, ceramics, glassceramics, mineral based materials and textiles. The compositions areespecially useful as coatings for synthetic organic polymeric substratesin sheet or film form, such as acrylic polymers,poly(ethyleneterephthalate), polycarbonates, polyamides, polyimides,copolymers of acrylonitrile-styrene, styrene-acrylonitrile-butadienecopolymers, polyvinyl chloride, butyrates, polyethylene and the like.Transparent polymeric materials coated with these compositions areuseful as flat or curved enclosures, such as windows, skylights andwindshields, especially for transportation equipment. Plastic lenses,such as acrylic or polycarbonate ophthalmic lenses, can also be coatedwith the compositions of the invention.

By choice of proper formulation, application conditions and pretreatment(including the use of primers) of the substrate, the coatingcompositions of the present invention can be adhered to substantiallyall solid surfaces. Abrasion resistant coatings having Bayer numbers ofat least 5 employing the test method hereinbefore described can beobtained by heat curing at temperatures in the range of 50° C. to 200°C. for a period of from about 5 minutes to 18 hours. The coatingthickness can be varied by means of the particular applicationtechnique, but coatings having a thickness of from about 0.5 to 20microns, and more desirably from about 1-10 microns, are generallyutilized.

In order to further illustrate the present invention, the followingexamples are given. However, it is to be understood that the examplesare for illustrative purposes only and are not to be construed aslimiting the scope of the subject invention The abrasion resistantproperties of the coatings produced by curing the coating compositionsprepared in accordance with the following examples were determined usingthe modification of the Oscillating Sand Test method (ASTM F735-81)hereinbefore described.

EXAMPLES Procedures

A. Etched poly(diethylene glycol-bis-allyl carbonate) lenses (referredto as ADC lenses) were used for coating and testing. The ADC lenses wereetched by contact with a 10% potassium hydroxide solution containingpropylene glycol methyl ether and water for a period of about 10minutes. The propylene glycol methyl ether and water were present in thepotassium hydroxide solution in a 1:1 volume ratio. The coating of thelenses with the coating compositions was achieved by dip coating theetched lenses at a withdrawal rate of 6 inches per minute. The coatedlenses were then cured at 120° C. for 3 hours. The lenses were testedusing the variation of the Oscillating Sand Test method hereinbeforedescribed and a Bayer number was determined for each coating.

B. Primed polycarbonate lenses (referred to as PC lenses) were used forcoating and testing. The PC lenses were primed with SDC Primer XF-1107(commercially available from SDC Coatings, Inc., Anaheim, Calif.) usinga withdrawal rate of 2 inches per minute followed by a 30 minute air dryto provide about a 0.5 micron prime coat. The coating of the lenses withthe coating compositions was achieved by dip coating the primed lensesat a withdrawal rate of 18 inches per minute. The coated lenses werethen cured at 130° C. for 4 hours. The lenses were tested using thevariation of the Oscillating Sand Test method hereinbefore described anda Bayer number was determined for each coating.

Example 1A

464 grams of 3-glycidoxypropyltrimethoxysilane were added slowly to 767grams of deionized water while stirring. The aqueous3-glycidoxypropyltrimethoxysilane mixture was stirred for approximatelyone hour. 69.6 grams of itaconic acid dissolved in 767 grams ofpropylene glycol methyl ether were then added streamwise to the aqueous3-glycidoxypropyltrimethoxysilane mixture. The mixture was then stirredfor 30 minutes, and then 1021 grams of tetraethyl orthosilicate wereslowly added to provide a resulting admixture which was stirredovernight to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 6.7.

Example 1B

380 grams of the coating composition from Example 1A were treated with0.9 grams of benzyldimethylamine and stirred for about 2 hours toproduce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.3 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 8.3.

Example 1C

380 grams of the coating composition from Example 1A were treated with1.2 grams of a 19% aqueous solution of sodium hydroxide to produce acoating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.4 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 10.5.

Examples 1B-1C illustrate the optional use of a catalyst with thecoating composition of Example 1A wherein the abrasion resistance isimproved when a catalyst is incorporated into the coating composition.

Example 2A

A) 496 grams of 3-glycidoxypropyltrimethoxysilane were added to 820grams of deionized water. The aqueous 3-glycidoxypropyltrimethoxysilanemixture was stirred for approximately one hour.

B) 200 grams of propylene glycol methyl ether and 18.2 grams of glutaricacid were added to 319 grams of the aqueous3-glycidoxypropyltrimethoxysilane mixture from step A above and stirredfor approximately 15 minutes to produce an admixture. 264.5 grams oftetraethyl orthosilicate were added to this admixture and stirredapproximately 17 hours to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 micron. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 7.9.

Example 2B

400 grams of the coating composition from Example 2A were treated with0.9 grams of benzyldimethylamine and stirred about 6 hours to produce acoating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 12.2.

Example 3A

200 grams of propylene glycol methyl ether and 13.7 grams of succinicanhydride were added to 319 grams of the aqueous3-glycidoxypropyltrimethoxysilane mixture (Step A) of Example 2A andallowed to stir for approximately 15 minutes to produce an admixture.264.5 grams of tetraethyl orthosilicate were added to the admixture andstirred for approximately 17 hours to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 6.2.

Example 3B

400 grams of the coating composition from Example 3A were treated with0.9 grams of benzyldimethylamine and stirred for approximately 6 hoursto produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 14.4.

Example 4A Comparative Example

116 grams of 3-glycidoxypropyltrimethoxysilane were added slowly to191.8 grams of deionized water. The aqueous3-glycidoxypropyltrimethoxysilane mixture was then stirred forapproximately one hour. 16 grams of acetic acid in 191.8 grams ofpropylene glycol methyl ether were then added streamwise to the aqueous3-glycidoxypropyltrimethoxysilane mixture. The mixture was then stirredfor 15 minutes, and 255.3 grams of tetraethyl orthosilicate were slowlyadded to provide a resulting admixture which was stirred approximately17 hours to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 4.4.

Example 4 in contrast with Examples 1A, 2A, and 3A shows the importanceof the multifunctional compound with respect to obtaining Bayer numbersof at least 5 when such coating compositions are tested using themodified Oscillating Sand Test method hereinbefore described.

Example 5

378 grams of 3-glycidoxypropyltrimethoxysilane were added to 653 gramsof deionized water and stirred for about 18 hours. 30.8 grams of a 12weight percent solution of itaconic acid in propylene glycol methylether were added to 98.5 grams of the aqueous3-glycidoxypropyltrimethoxysilane mixture with stirring. 100.8 grams oftetra-n-propyl orthosilicate were then added. The mixture was stirred 12hours and 19 grams of propylene glycol methyl ether were added toproduce a coating composition. The coating composition was aged 7 daysat 5° C.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 8.6.

Example 5 illustrates the use of a tetrafunctional silane other thantetraethyl orthosilicate and shows the generality of the presentinvention with respect to the tetrafunctional silane.

Example 6A Comparative Example

116 grams of 3-glycidoxypropyltrimethoxysilane were added to 191.8 gramsof deionized water. The aqueous 3-glycidoxypropyltrimethoxysilanemixture was stirred for approximately 1 hour. 17.4 grams of itaconicacid in 191.8 grams of propylene glycol methyl ether were addedstreamwise and stirred approximately 15 minutes to form an admixture.216.6 grams of Nalco N-1042 colloidal silica were added and stirredapproximately 17 hours to form a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about 2microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 3.0.

Example 6B Comparative Example

0.9 grams of benzyldimethylamine were added to 380 grams of the coatingcomposition of Example 6A and allowed to stir for about 2 hours to forma coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about 2microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 2.4.

Examples 6A and 6B illustrate the importance of the presence of thetetrafunctional silane in the coating compositions of the presentinvention with respect to obtaining Bayer numbers of at least 5 on thecured coating when such coating compositions are tested using themodified Oscillating Sand Test method hereinbefore described.

Example 7

118.5 grams of tetraethyl orthosilicate were added dropwise to 9.1 gramsof itaconic acid, 100.9 grams of water and 100.9 grams of propyleneglycol methyl ether, which were being stirred, to form anaqueous-organic solvent mixture. The aqueous-organic solvent mixture wasstirred for four hours. 67.2 grams of 3-glycidoxypropyltrimethoxysilanewere added dropwise and stirred about 14 hours to form an admixture.0.03 grams of a silicone leveling agent (PA-57 from Dow Corning,Midland, Mich.) in 0.27 grams of propylene glycol methyl ether wereadded to form a coating composition.

The coating composition was applied to primed PC lenses according toProcedure B to provide a cured coating. The coated lenses were thensubjected to the modified Oscillating Sand Test method hereinbeforedescribed and it was determined that the primed PC lenses coated withthe coating compositions prepared employing the procedures set forth inthis Example had a Bayer number of about 6.4.

Example 8

86.1 grams of tetraethyl orthosilicate were added dropwise to 10.6 gramsof itaconic acid, 112.5 grams of water and 112.5 grams of propyleneglycol methyl ether which were being stirred to form an aqueous-organicsolvent mixture. The aqueous-organic solvent mixture was stirred forfour hours. 78.3 grams of 3-glycidoxypropyltrimethoxysilane were addeddropwise and stirred about 14 hours to form an admixture. 0.03 grams ofa silicon leveling agent (PA-57) in 0.27 grams of propylene glycolmethyl ether were added to form a coating composition.

The coating composition was applied to the primed PC lenses according toProcedure B to provide a coating having a thickness of about 5.3microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the primed PC lenses coated with the coatingcompositions prepared employing the procedures set forth in this Examplehad a Bayer number of about 5.3.

Example 9

74.8 grams of tetraethyl orthosilicate were added dropwise to 9.1 gramsof itaconic acid, 114.6 grams of water and 114.6 grams of propyleneglycol methyl ether which were being stirred to form an aqueous-organicsolvent mixture. The aqueous-organic solvent mixture was stirred forfour hours. 84.8 grams of 3-glycidoxypropyltrimethoxysilane were addeddropwise and stirred about 14 hours to form an admixture. 0.03 grams ofa silicone leveling agent (PA-57) in 0.27 grams of propylene glycolmethyl ether were added to form a coating composition.

The coating composition was applied to the primed PC lenses according toProcedure B to provide a cured coating. The coated lenses were thensubjected to the modified Oscillating Sand Test method hereinbeforedescribed and it was determined that the primed PC lenses coated withthe coating compositions prepared employing the procedures set forth inthis Example had a Bayer number of about 5.4.

The following Examples 10A-12E illustrate process variations which canbe employed in the formulation of the compositions of the presentinvention having improved abrasion-resistance.

Example 10A

116.0 grams of 3-glycidoxypropyltrimethoxysilane, 255.3 grams oftetraethyl orthosilicate, 17.4 grams of itaconic acid and 191.8 grams ofpropylene glycol methyl ether were combined while being stirred into asingle mix. 191.8 grams of water were added to make a resulting mixture.The mixture was then stirred for 17 hours to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 7.5.

Example 10B

0.9 grams of benzyldimethylamine were added to 380 grams of the coatingcomposition of Example 10A and stirred for about 6 hours.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 10.7.

Example 11

45.4 grams of itaconic acid, 723.1 grams of propylene glycol methylether were combined with stirring to form a resulting mixture. 375.4grams of deionized water were then added to form an aqueous-organicsolvent admixture. 726.1 grams of tetraethyl orthosilicate were added tothe admixture and stirred 24 hours. 329.6 grams of3-glycidoxypropyltrimethoxysilane were then added to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about1.5 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 7.4.

Example 12A

A) 188.9 grams of tetraethyl orthosilicate were added to a mixture of212 grams of deionized water, 86.7 grams of propylene glycol methylether and 11.8 grams of itaconic acid and the resulting mixture wasstirred for 18 hours and stored at 50° C.

B) 476.8 grams of 3-glycidoxypropyltrimethoxysilane were added to 273.7grams of deionized water and the resulting mixture was stirred for 18hours and stored at 5° C.

C) 67.4 grams of the mixture produced in step B above were added to 250grams of mixture produced in step A above to produce a coatingcomposition. The coating composition was stirred for 24 hours.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about1.3 micron. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 9.3.

Example 12B

10.34 ml of an aqueous 0.105 molar sodium hydroxide solution were addedto 250 grams of mixture A from Example 12A above to a final pH of 3.4.The mixture was stirred for 18 hours. 67.4 grams of mixture B (Example12A) were then added to this mixture to produce an admixture. Theadmixture was stirred for 24 hours. A 163.9 gram aliquot of theadmixture was then diluted with 37.3 grams of propylene glycol methylether to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.4 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 13.9.

Example 12C

1312.1 grams of tetraethyl orthosilicate were added to a mixture of 82.1grams of itaconic acid, 639.1 grams of water, and 1005 grams ofpropylene glycol methyl ether to make an aqueous-organic solventmixture. This mixture was stirred for 18 hours. 115.4 grams of mixture Bin example 12A above were added to 364.6 grams of the aqueous-organicsolvent mixture. The mixture was stirred for 18 hours to produce acoating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating. The coated lenses were thensubjected to the modified Oscillating Sand Test method hereinbeforedescribed and it was determined that the etched ADC lenses coated withthe coating composition prepared employing the procedures set forth inthis Example had a Bayer number of about 8.7.

Example 12D

Benzyldimethylamine was added dropwise to the coating compositiondescribed in Example 12C to yield a coating composition with a pH valueof 4.2.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about1.8 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 10.1.

Example 12E

1 molar aqueous sodium hydroxide solution was added dropwise to thecoating composition described in Example 12C to yield a coatingcomposition with a pH value of 3.6.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about1.7 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 10.3.

Examples 12D-12E illustrate the use of a catalyst with the fullyformulated coating of Example 12C.

Example 13

Following the procedure described in Example 1, 61.4 grams of3-glycidoxypropyltrimethoxysilane, 96.4 grams of water, 88.7 grams ofpropylene glycol methyl ether, 9.2 grams of itaconic acid and 128.3grams of tetraethyl orthosilicate were combined in an admixture. To thisadmixture, 13 grams of Nalco 1115 colloidal silica were added by pouringand stirred overnight to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about1.9 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 9.8.

Example 14

Following the procedure described in Example 1, 61.9 grams of3-glycidoxypropyltrimethoxysilane, 87.2 grams of water, 87.1 grams ofpropylene glycol methyl ether, 9.3 grams of itaconic acid and 116.1grams of tetraethyl orthosilicate were combined in an admixture. To thisadmixture, 38.7 grams of Nalco 1115 colloidal silica were added bypouring and stirred overnight to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.0 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 12.6.

Example 15

Following the procedure outlined in Example 1, 61.2 grams of3-glycidoxypropyltrimethoxysilane, 75.8 grams of water, 83.7 grams ofpropylene glycol methyl ether, 9.2 grams of itaconic acid and 101 gramsof tetraethyl orthosilicate were combined in an admixture. To thisadmixture, 64.7 grams of Nalco 1115 colloidal silica were added bypouring and stirred overnight to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 11.

Example 16

17.4 grams of itaconic acid, 106 grams of water and 225.9 grams ofpropylene glycol methyl ether were combined to form a mixture. 223.3grams of tetraethyl orthosilicate were added dropwise to the mixturewhile stirring to produce a first admixture. The first admixture wasthen stirred for approximately two hours. 61.4 grams of Nalco 1115colloidal silica were rapidly added by pouring to produce a secondadmixture. The second admixture was then stirred for about 15 minutesand 116 grams of 3-glycidoxypropyltrimethoxysilane were added dropwiseto provide a resulting third admixture which was stirred approximately14 hours. 0.06 grams of a silicone leveling agent (PA-57) in 0.5 gramsof propylene glycol methyl ether were added to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating. The coated lenses were thensubjected to the modified Oscillating Sand Test method hereinbeforedescribed and it was determined that the etched ADC lenses coated withthe coating composition prepared employing the procedures set forth inthis Example had a Bayer number of about 11.6.

Example 17

153.1 grams of 3-glycidoxypropyltrimethoxysilane were added slowly to181.1 grams of Nalco 1115 colloidal silica, 100.5 grams of water and 5grams of itaconic acid which were being stirred constantly. The aqueous3-glycidoxypropyltrimethoxysilane mixture was then stirred for one hour.324.4 grams of propylene glycol methyl ether and an additional 16 gramsof itaconic acid were added. 220 grams of tetraethyl orthosilicate werethen added to the mixture, followed by another 50 grams of propyleneglycol methyl ether and then stirred overnight to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.4 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 13.6.

Example 18

153.1 grams of 3-glycidoxypropyltrimethoxysilane were added slowly to amixture of 90.5 grams of Ludox HS-30 colloidal silica, (DuPont Company,Wilmington, Del.) 190 grams of water and 5 grams of itaconic acid whichwas being constantly stirred. The 3-glycidoxypropyltrimethoxysilanemixture was then stirred for approximately two hours. 325.4 grams ofpropylene glycol methyl ether and an additional 16 grams of itaconicacid were then added to the 3-glycidoxypropyltrimethoxysilane mixtureand stirred for an additional hour to produce an admixture. 110 grams oftetraethyl orthosilicate were slowly added to a 390 gram aliquot of theadmixture while the admixture was being constantly stirred. Theresulting mixture was stirred overnight to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.4 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 8.4.

Example 19

132.0 grams of tetraethyl orthosilicate were added to a solution of 12.6grams of itaconic acid in a mixture of 114.0 grams of isopropanol and114 grams deionized water. The mixture was stirred for 3 hours. 54.3grams of Ludox HS-30 colloidal silica were added followed by anadditional 80 grams of isopropanol. 91.8 grams of3-glycidoxypropyltrimethoxysilane were then added to this mixture andstirred for about 18 hours. 75 ppm of a silicon leveling agent (PA-57)were added to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about3.0 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 7.9.

Examples 13-19 illustrate the addition of colloidal silica to thecompositions of the present invention formulated from an epoxyfunctional silane, a tetrafunctional silane and a multifunctionalcompound to produce compositions which, upon curing, have improvedabrasive resistance properties.

Examples 16-19 also illustrate the optional use of two different typesof basic colloidal silica and possible variations in mixing sequences.

Example 20

18.9 grams of methyltrimethoxysilane were added slowly to 56.3 grams ofwater which was being constantly stirred. 19.8 grams of3-glycidoxypropyltrimethoxysilane were then added slowly to thissolution and stirred approximately one hour. 4.5 grams of itaconic acidpre-dissolved in 56.3 grams of propylene glycol methyl ether were addedto the mixture and stirred for an additional hour. 81.3 grams oftetraethyl orthosilicate were slowly added, stirred an additional twohours and the mixture then allowed to sit at ambient temperatureovernight. 1.4 grams of benzyldimethylamine were then added to theresultant product to produce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about3.4 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 10.8.

Example 20 illustrates the addition of a silane additive to thecompositions of the present invention formulated from an epoxyfunctional silane, a tetrafunctional silane, and a multifunctionalcompound.

Example 21

18.9 grams of methyltrimethoxysilane were added slowly to 33.5 grams ofNalco 1042 colloidal silica which was being constantly stirred. 19.8grams of 3--glycidoxypropyltrimethoxysilane were then added slowly tothis solution and stirred approximately one hour. 4.5 grams of itaconicacid pre-dissolved in 56.3 grams of propylene glycol methyl ether wereadded to the mixture. This mixture was allowed to stir for an additionalhour before slowly adding 40.7 grams of tetraethyl orthosilicate toproduce an admixture which was stirred an additional two hours and thenallowed to sit at ambient temperature overnight. 1.4 grams ofbenzyldimethylamine were added to the admixture to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about3.3 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 6.6.

Example 22

Following the procedure outlined in Example 21, 16.8 grams of Nalco 1042colloidal silica, 18.9 grams of methyltrimethoxysilane, 19.8 grams of3-glycidoxypropyltrimethoxysilane, 4.5 grams of itaconic acid, 56.3grams of propylene glycol methyl ether, 61.0 grams of tetraethylorthosilicate and 1.4 grams of benzyldimethylamine were combined toproduce a coating composition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about3.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 9.9.

Example 23

37.7 grams of 3-glycidoxypropyltrimethoxysilane were added slowly to82.1 grams of water which was constantly stirred. The aqueous3-glycidoxypropyltrimethoxysilane mixture was then stirred forapproximately one hour. 5.2 grams of itaconic acid pre-dissolved in 96.6grams of propylene methyl glycol ether were added to the mixture. Thesolution was then stirred for an additional two hours before adding 0.54grams of dimethyldimethoxysilane. This mixture was then stirred for 30minutes and 77.4 grams of tetraethyl orthosilicate were added to themixture to produce an admixture, then stirred an additional two hoursand allowed to sit at ambient temperature overnight. 0.6 grams ofbenzyldimethylamine were added to the admixture to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about3.1 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 11.5.

Example 24

Following the procedure outlined in Example 23, 37.7 grams of3-glycidoxypropyltrimethoxysilane, 82.1 grams of water, 5.2 grams ofitaconic acid, 96.6 grams of propylene glycol methyl ether, 2.7 grams ofdimethyldimethoxysilane, 77.4 grams of tetraethyl orthosilicate and 0.6grams of benzyldimethylamine were combined to produce a coatingcomposition.

The coating composition was applied to the etched ADC lenses accordingto Procedure A to provide a cured coating having a thickness of about2.6 microns. The coated lenses were then subjected to the modifiedOscillating Sand Test method hereinbefore described and it wasdetermined that the etched ADC lenses coated with the coatingcomposition prepared employing the procedures set forth in this Examplehad a Bayer number of about 8.6.

Changes may be made in the construction and the operation of the variouscomponents, elements and assemblies described herein and changes may bemade in the steps or the sequence of steps of the methods describedherein without departing from the spirit and scope of the invention asdefined in the following claims.

What is claimed:
 1. An article comprising: a substrate; and asubstantially transparent abrasion-resistant coating formed on at leastone surface of the substrate, the coating having a Bayer number of atleast 5, the coating being formed by curing a coating compositioncomprising an aqueous-organic solvent mixture applied to the surface ofthe substrate and wherein the aqueous-organic solvent mixture consistingessentially of: from about 10 to about 99.9 weight percent, based on thetotal solids of the composition, of hydrolysis products and partialcondensates of an epoxy functional silane and a tetrafunctional silanewherein the epoxy functional silane is present in a molar ratio to thetetrafunctional silane of from about 0.1:1 to about 5:1 and the solventcomponent of the aqueous solvent dispersion is compatible with the epoxyfunctional silane and the tetrafunctional silane; from about 0.1 toabout 30 weight percent of a multifunctional compound, based on thetotal solids of the composition, wherein the multifunctional compound isselected from the group consisting of multifunctional carboxylic acids,multifunctional anhydrides and mixtures thereof; and an amount of watersufficient to hydrolyze the epoxy functional silane and thetetrafunctional silane.
 2. The article of claim 1 wherein the epoxyfunctional silane is present in a molar ratio to the tetrafunctionalsilane of from about 0.1:1 to about 3:1.
 3. The article of claim 1wherein the solvent constituent of the aqueous-organic solvent mixtureis selected from the group consisting of an alcohol, an ether, a glycol,a glycol ether, an ester, a ketone, a glycolether acetate and mixturesthereof.
 4. The article of claim 3 wherein the aqueous-organic solventmixture further includes an effective amount of a catalyst to provideenhanced abrasion resistance to a coating produced by curing thecomposition.
 5. The article of claim 4 wherein the effective amount ofthe cataylst is from about 0.1 to about 10 weight percent, based on thetotal solids of the composition.
 6. The article of claim 5 wherein theaqueous-organic solvent mixture further includes from about 0.1 to about50 weight percent, based on the total solids of the composition, of amixture of hydrolysis products and partial condensates of silaneadditive represented by the formula R⁹ _(x)Si(OR¹⁰)_(4−x) where x is aninteger of 1, 2 or 3, R⁹ is H, an alkyl group containing from 1 to about10 carbon atoms, a functionalized alkyl group, an alkylene group, anaryl group, an alkyl ether group and combinations thereof, R¹⁰ is H, analkyl group containing from 1 to about 10 carbon atoms, an acetyl groupand combinations thereof.
 7. The article of claim 6 wherein theaqueous-organic solvent mixture further includes: an effective amount ofa leveling agent to spread the aqueous-organic solvent mixture on thesubstrate and provide substantially uniform contact of theaqueous-organic solvent mixture with the substrate.
 8. The article ofclaim 1 wherein the solvent constituent of the aqueous-organic solventmixture is an alcohol having the general formula ROH where R is an alkylgroup containing from 1 to about 10 carbon atoms.
 9. The article ofclaim 1 wherein the solvent constituent of the aqueous-organic solventmixture is selected from the group consisting of a glycol, an ether, aglycol ether and mixtures thereof having the formula R¹—(OR²)_(x)—OR¹where x is an integer of 0, 1, 2, 3 or 4, R¹ is H or an alkyl groupcontaining from 1 to about 10 carbon atoms and R² is an alkylene groupcontaining from 1 to about 10 carbon atoms and combinations thereof. 10.The article of claim 1 wherein the epoxy functional silane isrepresented by the formula R³ _(x)Si(OR⁴)_(4−x) where x is an integer of1, 2 or 3, R³ is H, an alkyl group, a functionalized alkyl group, analkylene group, an aryl group, an alkyl ether and combinations thereofcontaining from 1 to about 10 carbon atoms and having at least 1 epoxyfunctional group, and R⁴ is H, an alkyl group containing from 1 to about5 carbon atoms, an acetyl group, a —Si(OR⁵)_(3−y)R⁶ _(y) group where yis an integer of 0, 1, 2, or 3, and combinations thereof where R⁵ is H,an alkyl group containing from 1 to about 5 carbon atoms, an acetylgroup, another —Si(OR⁵)_(3−y)R⁶ _(y) group and combinations thereof, andR⁶ is H, an alkyl group, a functionalized alkyl group, an alkylenegroup, an aryl group, an alkyl ether and combinations thereof containingfrom 1 to about 10 carbon atoms.
 11. The article of claim 10 wherein thetetrafunctional silane is represented by the formula Si(OR⁷)₄ where R⁷is H, an alkyl group containing from 1 to about 5 carbon atoms andethers thereof, an (OR⁷) carboxylate, a —Si(OR⁸)₃ group where R⁸ is a H,an alkyl group containing from 1 to about 5 carbon atoms and ethersthereof, an (OR⁸) carboxylate, another —Si(OR⁸)₃ group and combinationsthereof.
 12. The article of claim 11 wherein the solvent constituent ofthe aqueous-organic solvent mixture is an alcohol having the generalformula ROH where R is an alkyl group containing from 1 to about 10carbon atoms.
 13. The article of claim 11 wherein the solventconstituent of the aqueous-organic solvent mixture is selected from thegroup consisting of a glycol, an ether, a glycol ether and mixturesthereof having the formula R¹—(OR²)_(x)—OR¹ where x is an integer of 0,1, 2, 3 or 4, R¹ is H or an alkyl group containing from 1 to about 10carbon atoms and R² is an alkylene group containing from 1 to about 10carbon atoms and combinations thereof.
 14. The article of claim 11wherein the amount of water present in the aqueous-organic solventdispersion is an amount sufficient to provide a substantiallyhomogeneous mixture of hydrolysis products and partial condensates ofthe epoxy functional silane and the tetrafunctional silane.
 15. Thearticle of claim 1 wherein the tetrafunctional silane is represented bythe formula Si(OR⁷)₄ where R⁷ is H, an alkyl group containing from 1 toabout 5 carbon atoms and ethers thereof, an (OR⁷) carboxylate, a—Si(OR⁸)₃ group where R⁸ is a H, an alkyl group containing from 1 toabout 5 carbon atoms and ethers thereof, an (OR⁸) carboxylate, another—Si(OR⁸)₃ group and combinations thereof.
 16. The article of claim 1wherein at least a portion of the solvent component of theaqueous-organic solvent mixture is generated during hydrolysis of theepoxy functional silane and the tetrafunctional silane.
 17. The articleof claim 1 wherein the aqueous-organic solvent mixture further includes:from about 0.1 to about 50 weight percent, based on the total solids ofthe composition, of a mixture of hydrolysis products and partialcondensates of a silane additive represented by the formula R⁹_(x)Si(OR¹⁰)_(4−x) where x is an integer of 1, 2 or 3, R⁹ is H, an alkylgroup containing from 1 to about 10 carbon atoms, a functionalized alkylgroup, an alkylene group, an aryl group, an alkyl ether group andcombinations thereof, R¹⁰ is H, an alkyl group containing form 1 toabout 10 carbon atoms, an acetyl group and combinations thereof.
 18. Thearticle of claim 17 wherein the aqueous-organic solvent mixture furtherincludes: an effective amount of a leveling agent to spread theaqueous-organic solvent mixture on the substrate and providesubstantially uniform contact of the aqueous-organic solvent mixturewith the substrate.
 19. The article of claim 1 wherein theaqueous-organic solvent mixture further includes: from about 0.1 toabout 50 weight percent, based on the total solids of the composition,of a mixture of hydrolysis products and partial condensates of a silaneadditive represented by the formula R⁹ _(x)Si(OR¹⁰)_(4−x) where x is aninteger of 1, 2 or 3, R⁹ is H, an alkyl group containing from 1 to about10 carbon atoms, a functionalized alkyl group, an alkylene group, anaryl group, an alkyl ether group and combinations thereof, R¹⁰ is H, analkyl group containing from 1 to about 10 carbon atoms, an acetyl groupand combinations thereof; and an effective amount of colloidal silica toprovide the composition with from about 0.1 to about 50 weight percentsilica, based on the total of solids present in the composition.
 20. Thearticle of claim 19 wherein the aqueous-organic solvent mixture furtherincludes an effective amount of a catalyst to provide enhanced abrasionresistance to a coating produced by curing the composition.
 21. Thearticle of claim 20 wherein the effective amount of the catalyst is fromabout 0.1 to about 10 weight percent, based on the total solids of thecomposition.
 22. The article of claim 21 wherein the aqueous-organicsolvent mixture further includes: an effective amount of a levelingagent to spread the aqueous-organic solvent mixture on the substrate andprovide substantially uniform contact of the aqueous-organic solventmixture with the substrate.
 23. The article of claim 1 wherein theaqueous-organic solvent mixture further includes: an effective amount ofcolloidal silica to provide the composition with from about 0.1 to about50 weight percent silica, based on the total of solids present in thecomposition.
 24. The article of claim 23 wherein the aqueous-organicsolvent mixture further includes: an effective amount of a levelingagent to spread the aqueous-organic solvent mixture on the substrate andprovide substantially uniform contact of the aqueous-organic solventmixture with the substrate.
 25. The article of claim 24 wherein theamount of water present in the aqueous-organic solvent mixture is anamount sufficient to provide a substantially homogeneous mixture ofhydrolysis products and partial condensates of the epoxy functionalsilane and the tetrafunctional silane.
 26. The article of claim 25wherein the aqueous-organic solvent mixture further includes aneffective amount of a catalyst to provide enhanced abrasion resistanceto the coating produced by curing the aqueous solvent mixture.
 27. Thearticle of claim 26 wherein the effective amount of catalyst present inthe aqueous-organic solvent mixture is from about 0.1 to about 10 weightpercent, based on the total solids of the aqueous-organic solventmixture.
 28. The article of claim 26 wherein the aqueous-organic solventmixture further includes from about 0.1 to about 50 weight percent,based on the total of solids of the aqueous-organic solvent mixture, ofa mixture of hydrolysis products and partial condensates of a silaneadditive represented by the formula R⁹ _(x)Si(OR¹⁰)_(4−x) where x is aninteger of 1, 2 or 3, R⁹ is H, an alkyl group containing from 1 to about10 carbon atoms, a functionalized alkyl group, an alkylene group, anaryl group, an alkyl ether group and combinations thereof, R¹⁰ is H, analkyl group containing from 1 to about 10 carbon atoms, an acetyl groupand combinations thereof.
 29. The article of claim 1 wherein theaqueous-organic solvent mixture further includes: an effective amount ofa leveling agent to spread the aqueous-organic solvent mixture on thesubstrate and provide substantially uniform contact of theaqueous-organic solvent mixture with the substrate.
 30. The article ofclaim 1 wherein the substrate is formed of plastic, wood, ceramic, glassceramic, glass, mineral based, leather, paper, textile and metalmaterials.
 31. An article comprising: a substrate; and a substantiallytransparent abrasion-resistant coating formed on at least one surface ofthe substrate, the coating having a Bayer number of at least 5, thecoating being formed by curing a coating composition comprising anaqueous-organic solvent mixture applied to the surface of the substrate,the aqueous-organic solvent mixture consisting essentially of:hydrolysis products and partial condensates of an epoxy functionalsilane, a tetrafunctional silane and a multifunctional compound, whereinthe multifunctional compound is selected from the group consisting ofmultifunctional carboxylic acids, multifunctional anhydrides andcombinations thereof and wherein the epoxy functional silane is presentin a molar ratio to the tetrafunctional silane of from 0.1:1 to about5:1; and an amount of water sufficient to hydrolyze the epoxy functionalsilane and the tetrafunctional silane.